The City of Ember

Ember is a city built underground, lit by great lamps and powered by one huge generator. Its people have lived there for more than two hundred years, sheltered by the Builders until the surface should be safe again. The instructions for leaving were lost generations back, and now the generator is failing. The lamps flicker for longer each year, and the storerooms are close to empty.

Twelve-year-old Lina Mayfleet swaps job assignments with her friend Doon Harrow. She ends up running messages through the dim streets, while he takes the pipeworks work that was meant to be hers. At home, Lina comes across a torn, half-destroyed document that her family had kept. It appears to be a set of instructions written for the city's mayor long ago.

Lina and Doon work to put the broken message back together, sure that it holds the answer to Ember's survival. The mayor shows more interest in hoarding supplies than in dealing with the crisis, and the city's machinery keeps wearing down. The two friends have to find a way out before the light gives out completely.

This is a middle-grade adventure with a dystopian, mystery-driven premise. The mood is dim and tense, with the dwindling light setting the pace and the puzzle of the lost message driving the plot.